It is commonplace in the field of ophthalmology to topically apply medication a patient's eye by applying a fluid onto the surface of the cornea of the eye. Due to the ease of administration; eye drops are administered to the lower fornix, the potential space between the eye and the lower lid. Recent research has indicated more used efficiency with eye drops placed into the upper fornix, the potential space between the eye and the upper lid, using conventional eye drop dispensers in order to apply drops under the upper lid, the patent will be placed in a supine position or will need to put his/her head back while facing the ceiling. For some patients this can be a problem due to physical infirmities, the lack of a bed to lie on, hand tremor and the difficulties with hand eye coordination. Another problem with the usual method of applying topical medicine is the use of preservatives which may irritate the eye and cause tearing with subsequent decrease in efficiency of the medication due to "washout."
In addition to the application problems traditionally associated with the use of eye droppers is the amount of medication needed to achieve a certain result. Studies have shown that if eye medication is applied beneath the superior fornix of a patient, the medication will have an increased absorption rate and increased duration. A recent article discussing this issue was published in the Journal of Ocular Pharmacology, by Vincent H. L. Lee, dated May 25, 1990. According to Dr. Lee, for the last twenty years the main effort has been to design systems to prolong the residence time of topically applied drugs in the conjunctival sac. The approach has been to minimize precorneal drug loss through prolongation of residence time of the drug in the conjunctival sac. The major route by which most ophthalmic drugs enter the eye is traditionally believed to be via the cornea. There is increasing evidence which shows that topically applied ophthalmic drugs can reach the posterior of the eye by diffusion across the conjunctiva-sclera laminate. This route is favored because there are drugs which are poorly absorbed by the cornea compared to a more posterior route, such as some anti-glaucoma medication. Micro-particulate systems, such as nanoparticles and microspheres, may favor non-corneal drug penetration since they may accumulate in the fornices. The present invention provides an ophthalmic drug delivery system specifically designed to promote non corneal drug penetration. As well as a prolonged and more effective method of corneal absorption through the upper fornix, lid administration.
For many patients an improved drug delivery system for ophthalmic drugs may be of critical importance. Medication which is absorbed through the eye will commingle with other medicines present in a patient's system. The combination of certain types and levels of medication can be problematic for the patient. However, this problem can be lessened by using eye medications which are applied in doses which are efficacious yet smaller than the amount which is used with current eye droppers.
Another problem with the use of eye droppers is sterility. When a dropper is used and then replaced back in its container, there is a chance that the medication could become contaminated. Currently applied medications require the use of a preservative in order to maintain their safe use and effectiveness including medicines that are designed for use in ocular insert devices. This is problematic since some patients have an allergic reaction or chemical reaction to the preservative contained in the medicine. This type of allergic reaction causes "washing out" of the medication due to the severe tearing of the eye.
Another problem with medications which are supplied in drop form or in a continuous use device, is the occurrence of side effects. Depending upon the makeup of a particular patient, some types of medication can cause psychosis, heart problems and even a accidental heart attack due to systemic side effects. Lower lid application of medications may be absorbed systematically especially after entering the nasal mucosa.